bone and joint infection Flashcards
What is osteomyelitis
Bone infection
What is septic arthritis
joint infection
Who is most at risk of acute osteomyelitis
Children
Males
History of trauma
Adults with other diseases such as diabetes which cause immunosuppression
People who have had sickle cell disease
How does the infection begin in acute osteomyelitis
Most commonly the infection is somewhere in the body and haematogenously spreads to the bone
There can be local spread from a continuous site of infection e.g open fracture
People with poor vasculation are prone to infections of the bone
In infants what is the source of infection for osteomyelitis
Infected umbilical cord
In children what is the most common sources of infection in osteomyelitis
Boils
Tonsilitis
Skin abrasions
Chicken pox
In adults what is the most common source of infection for osteomyelitis
UTI, arterial line, chest infection, gall bladder infection
What is the most common organism which causes the osteomyelitis
Staphylococcus aureus
What are the common organisms which cause osteomyelitis in infants
Staph aureus
Group B strep
E.coli
What are the common organisms which cause osteomyelitis older children
Staph aureus
Strep pyogenes
Haemophilus influenza
What are the common organisms which cause osteomyelitis in adults
Staph aureus
coagulase negative staphylococci
What bones is acute osteomyelitis most common in and why
Long bones, specifically the metaphysis e.g distal femur, proximal tibia and proximal humerus
This is because they have a larger blood supply since they are larger
Describe how osteomyelitis occurs - infection moving through blood to bone
The infection clumps and then travels in the circulation - it gets stuck like an arterial thrombus - causes the build up of back pressure - lymphocytes are sent there but this causes pus which causes more pressure - the pressure needs released so infection enters the bone
What causes pain in bone when there is increase in pressure
Pressure receptors in the bone
What are the 3 sites where infection can infiltrate the bone
medulla, sub-periosteal or into joint resolution
What is a sequestrum
isolated piece of bone which has undergone necrosis due to no blood supply
What is involucrum
Formation of new bone
What are the clinical features of acute osteomyelitis in infants
May be minimal or very ill
Drowsy or irritable and not feeding
Pseudoparalysis - not moving a limb
Tendon at the bone with swelling
reduction of movement
Commonest at the knee
What are the clinical features of acute osteomyelitis in children
Severe pain
Reluctant to move
Pyrexia and tachycardia
Malaise
Toxaemia
What are the clinical features of acute osteomyelitis in adults
Backache - unremitting and at rest
History of UTI or urological procedure
Usually immunocompromised
What is the most common osteomyelitis location in adults
Thoracolumbar spine
How is osteomyelitis diagnosed (what are the investigations done)
History and clinical examination
FBC +WBC
ESR +CRP - inflammation markers
Blood cultures
U&Es
X-ray
US
bone biopsy
MRI
What is the differential diagnosis of osteomyelitis (other diagnosis options)
Soft tissue infection - cellulitis
Acute septic arthritis
Trauma
acute inflammatory arthritis
transient synovitis
What is the treatment of acute osteomyelitis
Antibiotics are the main treatment - IV because the bone isolates the infected blood supply
Analgesia and fluids for pain and dehydration (supportive treatment)
Surgery - not common
What is the indication for surgery in acute osteomyelitis
Aspiration of pus and abscess draining from bone via drilling into bone if pyrexia is prolonged after antibiotic treatment
What are the complications of acute osteomyelitis
Metastatic infection - infection spreads to different areas of the body
Pathological fracture
Septic arthritis
Septicemia
Altered bone growth through damaged epiphyseal growth plate
Chronic osteomyelitis
What organisms cause chronic osteomyelitis
Usually mixed but mainly staph aureus
Other common are E.coli, strep pyogenes and proteus
What is the treatment of chronic osteomyelitis
Local antibiotics - gentamicin cement
Systemic antibiotics - orally/IV
To try to cure - surgical eradication of the dead bone which is infected
What are the complications of osteomyelitis
Chronically discharging sinus
Metastatic infection
pathological fracture
growth disturbance and deformities
Squamos cell carcinoma
What is the route of infection of septic arthritis
Haematogenous
eruption of bone abscess
Direct invasion - penetrating wound
What are the common organisms that cause septic arthritis
Mainly Staph aureus
Haemophilus influenzae
Strep pyogenes
E.coli
What happens in acute septic arthritis
Acute synovitis and purulent joint effusion
Articular cartilage attacked by bacterial toxin and cellular enzymes
Complete destruction of articular cartilage
How does septic arthritis present in neonates
Irritabile
Resistance to joint movement
How does septic arthritis present in children and adults
Severe acute pain in a single large joint
Reluctancy to move the joint
swelling
erythema in the later stage
pyrexia and tachycardia
tenderness
What is the differential diagnosis for septic arthritis
Acute osteomyelitis
trauma
irritable joint
hameophilia
rheumatic fever
gout
Gaucher’s disease
What is one of the most common causes of acute septic arthritis in adults
Infected joint replacement
What is the treatment for acute septic arthritis
Antibiotics for 3-4 weeks
supportive measure - analgesia and fluids
Surgical drainage to let pus out the joint
Why is TB a great mimic
Presents in different forms and can present in the joint and as osteomyelitis
What are the clinical features of TB
insidious onset & general ill health
contact with TB
pain (esp. at night), swelling, loss of weight
low grade pyrexia
joint swelling
decrease ROM
ankylosis
Progressive deformity
What is ankylosis
stiffness of the joint
describe how TB spreads in the body
Starts in the gut or the lungs usually - then spreads elsewhere and commonly lodges into the vertebral joint and infects it
What are the signs seen in TB for diagnosis
Long history
Single joint involvement
Thickened synovium
Marked muscle wasting
Periarticular osteoporosis
What is periarticular osteoporosis
Low bone mass around a joint
What are the investigations done for TB
FBC,ESR - elevated
Mantoux test - tuberculin is put in the skin and causes red colour around it
Sputum/urine culture
Increased white cell count
X-ray
Joint aspiration and biopsy
What is the treatment of TB
Mainly antibiotics
Initially - rifampicin, isoniazid, ethambutol and then rifampicin and isoniazid for 8 weeks
Then prolonged treatment of rifampicin and isoniazid for 6-12 months
